1. Field of the Invention
This invention relates to a medical X-ray radiation power supply apparatus quickly raising a tube voltage to a predetermined value by using a DC-operated switching power supply in a dental or breast X-ray photographing apparatus.
2. Prior Act
The AC power supplies have been previously used in a dental or breast apparatus. However, the apparatus cannot deliver stable X-ray energy. Recently, an apparatus and technology using DC power supply to control an X-ray radiation has been disclosed. For example, the Patent Application No. 53-17066 (Japanese Provisional Publication No. 54-112190) discloses a technology of a DC-operated switching power supply. This method relates to a panoramic X-ray photograph apparatus for entire jaws, and it takes more than several hundred milliseconds until X-rays reach the predetermined value after an X-ray radiation start switch is turned on. This time period causes no problem since the photographing is done within approximately 10 to 20 seconds.
However, in a case of dental X-ray photograph apparatus, except a panoramic X-ray photograph apparatus for entire jaws, the shortest photographing time is approximately 0.1 to 0.2 seconds. When the tube voltage rising time for an X-ray radiation is long, compared with the short photographing time, the obtained results have considerable errors.
Regarding the medical X-ray photograph apparatus technology identical to the present invention, an X-ray power supply circuit using DC-operated phase control is also disclosed by the Utility Model Application No. 55-16078 (Japanese Provisional Publication No. 56-118607). This circuit has the disadvantages that an overshoot occurs and the linearity between the rise of tube voltage and radiation time is not satisfactory.